1. Field of the Invention
The present invention relates to a vehicle headlamp and more particularly to a shade that is installed in the vehicle headlamp.
2. Prior Art
Recently, an increasing number of vehicle headlamps are provided with a shade so that the driver of an oncoming vehicle or a pedestrian is not blinded by glare.
FIG. 5 shows the typical conventional shade structure.
The shade 2 is composed of a shade body 2A and a mount stay 2B. The shade body 2A surrounds the front end of a light source bulb 4 around an optical axis Ax1 like a cylinder, and the mount stay 2B supports the shade body 2A by being fixed to a reflector 6. The shade body 2A allows the incidence of only the direct light irradiated from the light source bulb 4 toward a reflective surface 6a of a reflector 6. The shade body 2A shades the light rays that might cause glare that includes, for example, a direct light irradiated upward in the forward direction from the light source bulb 4 and a direct light admitted onto the upper wall surface 6b of the reflector 6.
The rear expansion angle 2 that is broadened rearward relative to the optical axis Ax of the shade body 2A of the shade 2 is set to be a larger value (about 10xc2x0 or greater). If the rear expansion angle 2 is set to be a smaller value as shown in FIG. 6, some of the light reflecting from the reflective surface 6a of the reflector 6 is admitted onto the upper outer circumferential surface 2Aa of the shade body 2A. Such reflected light may cause the light B2 directed upward to be irradiated to the fore of the lamp unit, thus generating glare.
The above-described setting of the rear expansion angle of FIG. 5 is made to prevent generation of the glare.
If the rear expansion angle 2 of the shade body 2A is set to be a large value as in FIG. 5, the light from the light source bulb 4 reflects off of the upper inner circumferential surface 2Ab of the shade body 2A and admitted onto the lower area of the reflective surface 6a of the reflector 6 as shown by the chain double-dashed line in FIG. 5. The resultant reflected light causes the light B1 that is directed upward, which causes the glare, to be irradiated to the fore of the lamp unit.
One solution to overcome the above problems is to coat the inner surface of the shade body 2A with black paint so as to eliminate the reflection by the upper inner circumferential surface 2Ab, thus preventing the irradiation of the upwardly directed light B1 to the fore of the lamp unit. The application of this black paint coating, however, creates another problem. It increases the manufacturing cost of the shade.
Moreover, in the shade 2 above, the rear expansion angle 2 of the shade body 2A has to be set to a substantially large value. However, this structure would restrict the degree of freedom in designing the shape of the shade.
In view of the above, the object of the present invention is to provide a vehicle headlamp having a shade, in which the cost of the shade can be reduced and the degree of freedom in the shaping thereof can be improved.
So as to accomplish the object, the present invention provides a novel surface shape for the shade.
More specifically, the present invention is for a vehicle headlamp that includes a light source bulb installed on an optical axis that extends in the longitudinal direction of the vehicle, a reflector having a reflective surface for reflecting the light from the light source bulb forward, and a shade for blocking some of the light directly irradiated from the light source bulb; and in the present invention, the shade is comprised of a shade body and a mount stay, the shade body surrounding the front-end portion of the light source bulb around the optical axis like a cylinder, and the mount stay supporting the shade body; and the outer circumferential surface of the shade body has a corrugated diffusion portion so as to diffusely reflect the light admitted thereto.
The xe2x80x9cshade bodyxe2x80x9d is formed of only a cylinder-like portion that surrounds the front end of the light source bulb around the optical axis like a cylinder. Alternatively, it can be formed in a cap-like shape so as to block the front end of the cylinder-like portion.
The xe2x80x9cupper outer circumferential surfacexe2x80x9d refers to the outer circumferential surface of the upper portion of the shade body. The xe2x80x9cupper portion of the shade bodyxe2x80x9d designates the area that crosses over left and right from a position directly above the optical axis of the shade body. The area of the upper portion of the shade body is not particularly limited to be a certain range.
The configuration, size or the like of the above-described xe2x80x9ccorrugated diffusion portionxe2x80x9d are not particularly limited as long as it has a plurality of repeating concave and convex portions to cause the light admitted onto the upper outer circumferential surface of the shade body to be diffusely reflected. In other words, the corrugated diffusion portion has a configuration of, for instance, a wave-like corrugated surface, mesh-like corrugated surface, dot-like corrugated surface, mat-like corrugated surface and the like.
The vehicle headlamp of the present invention is provided with a shade that blocks some of the direct light irradiated from the light source bulb. The shade body of the shade surrounds the front end of the light source bulb like a cylinder. The corrugated diffusion portion is formed on the upper outer circumferential surface of the shade body so that the light admitted onto the upper outer circumferential surface is diffusely reflected. Because of this structure, the following advantageous effect can be obtained.
Even if some of the light reflected from the reflective surface of the reflector is admitted onto the upper outer circumferential surface of the shade body, the light reflected therefrom becomes a diffused light by the diffusion reflection function of the corrugated diffusion portion. As a result, the light directed upward which is irradiated to the fore of the lamp unit can be lowered in its intensity to a substantially small value, thus eliminating the glare.
Although some of the light reflected from the reflective surface of the reflector is admitted onto the upper outer circumferential surface of the shade body, no glare is likely to occur. Therefore, the rear expansion angle of the shade body does not have to be set to a larger value as in the case of the prior art, thus enhancing the degree of freedom in shaping the shade.
In the present invention, the rear expansion angle of the shade body is set to be a small value. The shade is thus shaped so that the light from the light source bulb reflected from the upper inner circumferential surface of the shade body is not admitted onto the lower area of the reflective surface of the reflector (to minimize the quantity of light) Accordingly, the generation of glare due to the light reflecting off of the inner surface of the shade can be preliminarily prevented without applying a black paint coating to the inner surface of the shade body. The cost of the shade thus can be reduced by the amount corresponding to the cost that can be saved by eliminating the process for applying the black paint coating.
As seen from the above, the present invention provides a vehicle headlamp provided with a shade, in which the cost for the shade is reduced, and the degree of freedom in shaping the shade is improved.
In the above-described structure, it is possible to set the rear expansion angle of the shade body to be constant over the entire circumferential area. It is also possible to set the rear expansion angle differently at each position in the circumferential direction. In this case, it is preferable that the upper portion of the shade body is formed at a rear expansion angle of 7xc2x0 or less with respect to the optical axis. By way of this, incidence of the light reflecting from the upper inner circumferential surface of the shade body onto the lower area of the reflective surface of the reflector can be more effectively prevented.
It can be clearly understood that the structure of the xe2x80x9ccorrugated diffusion portionxe2x80x9d is not particularly limited. The sectional shape of the corrugated diffused portion that is perpendicular to the optical axis can be a longitudinally striped wave-like surface. With this longitudinally striped wave-like surface, the corrugated diffused portion can be formed without deteriorating its moldability in case the shade is formed by press molding a plate material. In case where a plurality of reflecting elements constitute the reflective surface of the reflector, the design of the reflecting elements can be easily matched with the design of the corrugated diffused portion.
By forming the corrugated diffused portion as a longitudinally striped wave-like surface, the upper inner circumferential surface of the shade body can be easily formed so as to have the longitudinally striped wave-like surface. With this structure, the light reflected from the upper inner circumferential surface could be formed into diffusely reflected light. Even if the rear expansion angle of the shade body is set to a large value, the black paint coating can be eliminated. In other words, the light from the light source bulb admitted to the upper inner circumferential surface of the shade body is admitted to the lower area of the reflective surface of the reflector as a diffusely reflected light. Therefore, the light directed upward to be irradiated to the fore of the lamp unit from the lower area can be reduced in its intensity to a substantially small value so as not to glare. It is thus possible to prevent a generation of glare that results from the light reflecting from the inner surface of the shade without applying a black paint coating thereto.
In the present invention, the structure of the reflective surface of the reflector is not particularly limited. The reflector may be formed so as to have a single curved surface like a paraboloid of revolution or the like. Alternatively, it may have a plurality of reflecting elements. In the latter case, the design of the lamp unit can be further unified by forming the surface configuration of the area above the optical axis on the reflective surface of the reflector to have a substantially identical configuration to that of the corrugated diffused portion. The term xe2x80x9cthe area above the optical axisxe2x80x9d refers to the area that crosses over left and right from a position directly above the optical axis on the reflective surface of the reflector. The angle of this area is not particularly restricted to be in the particular range.